Soft nitrided induction hardened steel part
View Patent ↗A soft nitrided induction hardened steel part which is excellent in bearing fatigue strength comprised of a predetermined chemical composition wherein a dissolved N concentration from the surface to 0.2 mm depth is 0.05 to 1.50%, a Vicker's hardness from the surface to 0.2 mm depth after tempering at 300° C. is HV 600 or more, and t/r≤0.35 when an effective hardened layer depth “t” is 0.5 mm or more and a radius of a breakage risk site or half of the thickness is “r” (mm).
1. A soft nitrided induction hardened steel part comprising:
a base material with a chemical composition consisting of, by mass %,
C: 0.30 to 0.80%,
Si: 0.02 to 2.5%,
Mn: 0.35 to 2.0%,
Al: 0.001 to 2.0%,
Cr: 0.01 to 3.0%,
S: 0.040% or less,
N: 0.0030 to 0.02%,
O: 0.005% or less
P: 0.025% or less,
Nb: 0.3% or less,
Ti: 0.3% or less,
V: 1.0% or less,
Ni: 3.0% or less,
Cu: 3.0% or less,
Co: 3.0% or less,
Mo: 1.0% or less,
W: 0.5% or less,
B: 0.005% or less,
Ca: 0.01% or less,
Mg: 0.01% or less,
Zr: 0.05% or less,
Te: 0.1% or less,
Pb: 0.5% or less,
REM: 0.005% or less, and
a balance of Fe and impurities, wherein
a concentration of dissolved N from the surface of the steel part to 0.2 mm depth is 0.05 to 1.50%,
a Vicker's hardness from the surface to 0.2 mm depth after tempering at 300° C. is HV 600 or more, and
an effective hardened layer depth “t” is 0.5 mm or more, a radius of a breakage risk site or half of a thickness is “r” in mm, and t/r≤0.35.
2. The soft nitrided induction hardened steel part according to claim 1 , wherein the base material consists of one or more of, by mass %, Nb: 0.005 to 0.3%, Ti: 0.005 to 0.3%, V: 0.01 to 1.0%, Ni: 0.01 to 3.0%, Cu: 0.01 to 3.0%, Co: 0.01 to 3.0%, Mo: 0.01 to 1.0%, W: 0.03 to 0.5%, B: 0.0006 to 0.005%, Ca: 0.0005 to 0.01%, Mg: 0.0005 to 0.01%, Zr: 0.0005 to 0.05%, Te: 0.0005 to 0.1%, Pb: 0.0005 to 0.5% and REM: 0.0005 to 0.005%.